In a 6 to 8-quart, heavy-bottomed saucepan, heat olive oil and butter over medium heat. Add onion, celery, carrot and garlic and sweat over medium heat until vegetables are translucent. Add veal, pork, beef and pancetta and stir into vegetables. Brown over high heat, stirring to keep meat from sticking together. This should take 15 to 20 minutes. Add the milk and simmer until reduced to nothing, about 10 minutes. Add tomatoes and simmer 15 minutes. Add the wine and brodo, bring to a boil, lower the heat and simmer over for 2 to 2 1/2 hours. Season with salt and pepper, to taste and remove from heat.